A lower bound to the spectral threshold in curved tubes

We consider the Laplacian in curved tubes of arbitrary cross-section rotating together with the Frenet frame along curves in Euclidean spaces of arbitrary dimension, subject to Dirichlet boundary conditions on the cylindrical surface and Neumann conditions at the ends of the tube. We prove that the spectral threshold of the Laplacian is estimated from below by the lowest eigenvalue of the Dirichlet Laplacian in a torus determined by the geometry of the tube.Comment: LaTeX, 13 pages; to appear in R. Soc. Lond. Proc. Ser. A Math. Phys. Eng. Sc

Phase Transition and Monopoles Densities in a Nearest Neighbors Two-Dimensional Spin Ice Model

In this work, we show that, due to the alternating orientation of the spins in the ground state of the artificial square spin ice, the influence of a set of spins at a certain distance of a reference spin decreases faster than the expected result for the long range dipolar interaction, justifying the use of the nearest neighbor two dimensional square spin ice model as an effective model. Using an extension of the model presented in ref. [Scientific Reports 5, 15875 (2015)], considering the influence of the eight nearest neighbors of each spin on the lattice, we analyze the thermodynamics of the model and study the monopoles and string densities dependence as a function of the temperature.Comment: 11 pages, 8 figure

Categorização das respostas às questões do questionário views on science-technology-society (vosts) realizada por professores/pesquisadores brasileiros

Esta pesquisa contou com a colaboração de 22 professores/pesquisadores brasileiros das áreas de Ciências Humanas, Naturais e Exatas, que categorizaram as opções de respostas às questões do questionário Views on Science-Technology-Society (VOSTS) referentes às dimensões: Construção social da Tecnologia e Influência da Sociedade na Ciência e na Tecnologia. Esse processo consistiu em analisar opções de respostas das questões e as categorizarem em realista, plausível e simplista. Com esse método estabeleceu-se validez ao processo de categorização, pois este foi realizado pela comunidade científica. Com a análise dos dados constatou-se que não é simples observar consenso por parte dos analistas nas frases categorizadas em realista e plausível, visto que desde a construção do VOSTS as controvérsias em relação aos assuntos abordados em suas questões se ampliaram muito

Does e-learning policy drive change in Higher Education?: A case study relating models of organisational change to e-learning implementation

Due to the heightened competition introduced by the potential global market and the need for structural changes within organisations delivering e-content, e-learning policy is beginning to take on a more significant role within the context of educational policy per se. For this reason, it is becoming increasingly important to establish what effect such policies have and how they are achieved. This paper addresses this question, illustrating five ways in which change is understood (Fordist, evolutionary, ecological, community of practice and discourse-oriented) and then using this range of perspectives to explore how e-learning policy drives change (both organisational and pedagogic) within a selected higher education institution. The implications of this case are then discussed, and both methodological and pragmatic conclusions are drawn, considering the relative insights offered by the models and ways in which change around e-learning might be supported or promoted

Equilibrium configurations for quark-diquark stars and the problem of Her X-1 mass

We report new calculations of the physical properties of a quark-diquark plasma. A vacuum contribution is taken into account and is responsible for the appearance of a stable state at zero pressure and at a baryon density of about 2.2 times the nuclear matter density in this model. The resulting equation of state was used to integrate numerically the Tolman-Oppenheimer-Volkoff equations. The mass-radius relationship has been derived from a series of equilibrium configurations constituted by a mixture of quarks and diquarks. These stellar models, which are representative of a whole class, may be helpful to understand the possible compactness of the X-ray source Her X-1 and related objects.Comment: 15 pp., PlainTex file + 3 figures available upon request at [email protected]. Submitted to Int. Jour. Mod. Phys.

Diversidade cultural, virulência e agressividade de Rhizoctonia spp. em solos cultivados com feijoeiro comum.

Este trabalho teve como objetivo avaliar a diversidade cultural, a virulência e a agressividade de isolados de Rhizoctonia solani ao feijoeiro comum (Phaseolus vulgaris), provenientes de áreas com histórico de cultivo desta espécie

Modelling study of the impact of deep convection on the utls air composition - Part I: Analysis of ozone precursors

International audienceThe aim of this work is to study the local impact on the upper troposphere/lower stratosphere air composition of an extreme deep convective system. For this purpose, we performed a simulation of a convective cluster composed of many individual deep convective cells that occurred near Bauru (Brazil). The simulation is performed using the 3-D mesoscale model RAMS coupled on-line with a chemistry model. The comparisons with meteorological measurements show that the model produces meteorological fields generally consistent with the observations. The present paper (part I) is devoted to the analysis of the ozone precursors (CO, NOx and non-methane volatile organic compounds) and HOx in the UTLS. The simulation results show that the distribution of CO with altitude is closely related to the upward convective motions and consecutive outflow at the top of the convective cells leading to a bulge of CO between 7 km altitude and the tropopause (around 17 km altitude). The model results for CO are consistent with satellite-borne measurements at 700 hPa. The simulation also indicates enhanced amounts of NOx up to 2 ppbv in the 7–17 km altitude layer mainly produced by the lightning associated with the intense convective activity. For insoluble non-methane volatile organic compounds, the convective activity tends to significantly increase their amount in the 7–17 km layer by dynamical effects. During daytime in the presence of lightning NOx, this bulge is largely reduced in the upper part of the layer for reactive species (e.g. isoprene, ethene) because of their reactions with OH that is increased on average during daytime. Lightning NOx also impacts on the oxydizing capacity of the upper troposphere by reducing on average HOx, HO2, H2O2 and organic hydroperoxides. During the simulation time, the impact of convection on the air composition of the lower stratosphere is negligible for all ozone precursors although several of the simulated convective cells nearly reach the tropopause. There is no significant transport from the upper troposphere to the lower stratosphere, the isentropic barrier not being crossed by convection. The impact of the increase of ozone precursors and HOx in the upper troposphere on the ozone budget in the LS is discussed in part II of this series of papers